Traffic accidents often occur due to driver impairment caused by, for example, drowsiness. In order to prevent accidents caused by driver impairment, it may be vital to provide the driver with a warning message to re-establish the attention of the driver to the surrounding traffic situation, or in a critical situation to advice the driver to take a break or switch to another driver of the vehicle.
Recently, much progress has been made in developing drowsiness detection algorithms that are based on detection of the driver's eye closure with a monitoring sensor, e.g. a camera or the like. These algorithms may be used in an image input unit that, by use of the monitoring sensor, detects the face and eyes of the driver. Hereby, the driver's gaze direction can be detected, e.g. the direction in which the driver of the vehicle is currently looking.
An example of a system having an image input unit can be found in US 2003/039 378. The image input unit of US 2003/039 378 inputs an image including the driver's face area to specify the driver's gaze or face direction. The system generates an input pattern based on the received image input, for determining the driver's gaze or face direction. Moreover, there is provided a dictionary pattern comprising a plurality of stored targets, i.e. positions inside and outside the vehicle which the driver have looked at in the past. The targets may, for example, be the side mirrors, back mirror, infotainment system, etc. Furthermore, the input pattern generated by the system is compared to the stored targets in order to determine the current gaze or face direction of the driver.
However, even though the systems for detecting the driver's eyes have become more and more sophisticated, they do not take in account that there are other factors than drowsiness that may cause the driver to reduce the eye opening size or look away in a certain direction (e.g. due to changing lighting conditions within the vehicle compartment). This may, for example, also be caused by external factors such as direct sunlight, flickering light, headlights from oncoming traffic at nights, etc. Also, if the driver is looking down or sideways, the systems may detect this as an eye closure. There is hence a risk that the driver of the vehicle is provided with a warning message intended for a drowsy driver when, in fact, the driver is fully aware of the situation. It is therefore desirable to provide a method which discriminate between the actual factor(s) of a detected eye closure before a warning message is provided to the driver.